This invention relates to a vacuum generator and more particularly to a vacuum generator of the type generally referred to as a venturi block, vacuum venturi or vacuum ejector. In still greater particularity, the invention relates to a venturi block including means for breaking the vacuum at the vacuum port thereof and providing for what is commonly referred to as blowoff.
Venturi blocks are well known and work on the well known vacuum venturi principle wherein a low pressure area can be formed by passing a pressurized gas, such as air, through a venturi nozzle, which low pressure area can be used to pull a vacuum on some work piece or tool to be operated. Vacuum venturi blocks are used in a wide variety of applications including, for example, material handling systems requiring vacuum pickup of articles such as by a vacuum cup. In such systems, the venturi block generates a vacuum which is applied to the vacuum operated tool, in this case a vacuum cup, to perform the desired function. When the function has been completed, it is necessary to discontinue the vacuum and in many applications, and in particular material handling and article transfer systems, fast, alternating application and breaking of the vacuum is required to effect fast and efficient operation of the system. If the vacuum is not broken and relieved quickly, the speed of operation will be significantly reduced.
Heretofore, when it has been required to break the vacuum generated by the vacuum block, an auxiliary pressurized gas system including external lines associated valving and controls has been utilized to apply an auxiliary pressurized gas, such as air, either to the exhaust port of the venturi block or directly to a line connecting the vacuum ports from the venturi block to the vacuum operated tool or device. In either case, the vacuum venturi effect is upset through the introduction of the auxiliary pressurized gas, thereby preventing generation of vacuum by the venturi and, depending on the pressure of the auxiliary gas supply, a positive pressure can be quickly applied to the tool or the device to effect positive blowoff. The positive pressure is particularly effective for quickly releasing the hold of a vacuum cup. Such auxiliary vacuum break or blowoff means are operationally effective but are not cost effective to implement for they require additional gas supply lines, regulators and controls for each tool operated. It can be seen, that in large systems, the additional hardware adds significantly to the cost, complexity and required maintenance of the system.